Test mazer 'install' won't get Content not in the correct Distribution
This is the negative test related to https://pulp.plan.io/issues/4778
Add the collection to Pulp but do not have the collection served by a Distribution.
Try to have mazer install it and verify that it won't install even though the content unit is inside of Pulp (but not that Distribution).
This validates that content is only handed out through the correct Distributions.
I'm not sure if this is a very valuable test though since core is really providing this feature.